The dry bulb temperature lines, on the psychrometric chart are

horizontal and uniformly spaced

horizontal and non-uniformly spaced

In a psychrometric chart, specific humidity (moisture content) lines are

horizontal and non-uniformly spaced

horizontal and uniformly spaced

horizontal and non-uniformly spaced

In chemical dehumidification process,

dew point temperature decreases

In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by

absorber, generator and liquid pump

It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be

dehumidification and pure sensible cooling

The refrigerant supplied to a compressor must be

dry saturated liquid refrigerant

a mixture of liquid and vapour refrigerant

Thermal conductivity of a material may be defined as the

quantity of heat flowing in one second through a slab of the material of area 1 cm² and thickness 1 cm when its faces differ in temperature by 1° C

quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1° C

heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces

According to Newton's law of cooling, the heat transfer from a hot body to a cold body is

directly proportional to the surface area

directly proportional to the difference of temperatures between the two bodies

387 + Mcqs in Heat Transfer Refrigeration and Air Conditioning Page 5 McqOptions

201.	The lowest thermal diffusivity is of
A.	iron
B.	lead
C.	aluminium
D.	rubber
Answer» E.

Discussion

202.	According to Stefan's law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

203.	The dry bulb temperature lines, on the psychrometric chart are
A.	vertical and uniformly spaced
B.	horizontal and uniformly spaced
C.	horizontal and non-uniformly spaced
D.	curved lines
Answer» B. horizontal and uniformly spaced

Discussion

204.	The dry bulb temperature during sensible heating of air
A.	remains constant
B.	increases
C.	decreases
D.	None of these
Answer» C. decreases

Discussion

205.	During humidification process, dry bulb temperature
A.	remains constant
B.	increases
C.	decreases
D.	None of these
Answer» B. increases

Discussion

206.	A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be
A.	1.33
B.	2.33
C.	3.33
D.	4.33
Answer» C. 3.33

Discussion

207.	The thermal diffusivity for gases is generally __________ those for liquids.
A.	equal to
B.	less than
C.	greater than
D.	None of these
Answer» D. None of these

Discussion

208.	The boiling point of __________ is -10.5°C.
A.	ammonia
B.	R-12
C.	sulphur dioxide
D.	carbon dioxide
Answer» D. carbon dioxide

Discussion

209.	Air refrigerator works on
A.	reversed Carnot cycle
B.	Bell Coleman cycle
C.	both (a) and ib)
D.	none of these
Answer» D. none of these

Discussion

210.	During sensible cooling of air, specific humidity
A.	remains constant
B.	increases
C.	decreases
D.	None of these
Answer» B. increases

Discussion

211.	The radiation emitted by a black body is known as
A.	black radiation
B.	full radiation
C.	total radiation
D.	all of these
Answer» E.

Discussion

212.	In a vapour compression system, the condition of refrigerant is dry saturated vapour
A.	before entering the compressor
B.	after leaving the compressor
C.	before entering the condenser
D.	after leaving the condenser
Answer» B. after leaving the compressor

Discussion

213.	The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat.
A.	good
B.	bad
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

214.	Dehydration is the process of removing water vapour from the surrounding air.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» B. False

Discussion

215.	The sensible heat gain is due to the __________ difference between the fresh air and the air in space.
A.	temperature
B.	humidity
C.	Can't say
D.	None of these
Answer» B. humidity

Discussion

216.	The expression is used for calculating relative humidity.
A.	Yes
B.	No
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

217.	The specific humidity during cooling and dehumidification
A.	remains constant
B.	increases
C.	decreases
D.	None of these
Answer» D. None of these

Discussion

218.	In a psychrometric chart, dew point temperature lines are horizontal and non-uniformly spaced.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

219.	In a psychrometric chart, specific humidity (moisture content) lines are
A.	vertical and uniformly spaced
B.	horizontal and uniformly spaced
C.	horizontal and non-uniformly spaced
D.	curved lines
Answer» C. horizontal and non-uniformly spaced

Discussion

220.	A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is
A.	h1 + h2 + h3
B.	(h1h2h3)^1/3
C.	h1 + h2 - h3
D.	none of these
Answer» E.

Discussion

221.	The lowest temperature during the cycle in a vapour compression system occurs after
A.	compression
B.	expansion
C.	condensation
D.	evaporation
Answer» E.

Discussion

222.	In a refrigeration system, the expansion device is connected between the
A.	compressor and condenser
B.	condenser and receiver
C.	receiver and evaporator
D.	evaporator and compressor
Answer» D. evaporator and compressor

Discussion

223.	Which of the following refrigerant has the lowest freezing point?
A.	R-11
B.	R-12
C.	R-22
D.	Ammonia
Answer» D. Ammonia

Discussion

224.	A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» B. False

Discussion

225.	Hydrogen is used in electrolux refrigeration system so as to __________ the rate of evaporation of the liquid ammonia passing through the evaporator.
A.	equalise
B.	reduce
C.	increase
D.	None of these
Answer» D. None of these

Discussion

226.	The alignment circle is marked on the psychrometric chart at
A.	20°C DBT and 50% RH
B.	26°C DBT and 50% RH
C.	20°C DBT and 60% RH
D.	26°C DBT and 60% RH
Answer» C. 20°C DBT and 60% RH

Discussion

227.	A simple air cooling system is good for __________ flight speeds.
A.	low
B.	high
C.	Can't say
D.	None of these
Answer» B. high

Discussion

228.	In chemical dehumidification process,
A.	dew point temperature decreases
B.	wet bulb temperature decreases
C.	dry bulb temperature increases
D.	all of these
Answer» E.

Discussion

229.	In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by
A.	liquid pump
B.	generator
C.	absorber and generator
D.	absorber, generator and liquid pump
Answer» E.

Discussion

230.	The undesireable property of a refrigerant is
A.	non-toxic
B.	non-flammable
C.	non-explosive
D.	high boiling point
Answer» E.

Discussion

231.	The sensible heat during humidification process decreases.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

232.	An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be
A.	25 mm
B.	40 mm
C.	160 mm
D.	800 mm
Answer» B. 40 mm

Discussion

233.	The super-heating in a refrigeration cycle
A.	does not alter C.O.P.
B.	increases C.O.P.
C.	decreases C.O.P.
D.	none of these
Answer» D. none of these

Discussion

234.	The emissivity of a polished silver body is __________ as compared to black body.
A.	same
B.	low
C.	very low
D.	high
Answer» D. high

Discussion

235.	The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is
A.	high pressure saturated liquid
B.	wet vapour
C.	very wet vapour
D.	dry vapour
Answer» D. dry vapour

Discussion

236.	It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be
A.	dehumidification
B.	cooling and humidification
C.	cooling and dehumidification
D.	dehumidification and pure sensible cooling
Answer» D. dehumidification and pure sensible cooling

Discussion

237.	The refrigerant supplied to a compressor must be
A.	superheated vapour refrigerant
B.	dry saturated liquid refrigerant
C.	a mixture of liquid and vapour refrigerant
D.	none of these
Answer» B. dry saturated liquid refrigerant

Discussion

238.	The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and
A.	carbon dioxide
B.	sulphur dioxide
C.	lithium bromide
D.	R-12
Answer» D. R-12

Discussion

239.	The expansion valve in a refrigerator controls the flow of refrigerant.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

240.	In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about
A.	1
B.	1.25
C.	2.15
D.	5.12
Answer» C. 2.15

Discussion

241.	The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called
A.	humidity ratio
B.	relative humidity
C.	absolute humidity
D.	degree of saturation
Answer» E.

Discussion

242.	The overall coefficient of heat transfer is used in problems of
A.	conduction
B.	convection
C.	radiation
D.	conduction and convection
Answer» E.

Discussion

243.	Thermal conductivity of a material may be defined as the
A.	quantity of heat flowing in one second through a slab of the material of area 1 cm² and thickness 1 cm when its faces differ in temperature by 1° C
B.	quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1° C
C.	heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
D.	all of the above
Answer» E.

Discussion

244.	According to Newton's law of cooling, the heat transfer from a hot body to a cold body is
A.	directly proportional to the surface area
B.	directly proportional to the difference of temperatures between the two bodies
C.	either (a) or (b)
D.	both (a) and (b)
Answer» E.

Discussion

245.	In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is
A.	reversed Carnot cycle
B.	reversed Joule cycle
C.	reversed Brayton cycle
D.	reversed Otto cycle
Answer» D. reversed Otto cycle

Discussion

246.	A vapour absorption refrigerator uses __________ as a refrigerant.
A.	water
B.	ammonia
C.	freon
D.	aqua-ammonia
Answer» E.

Discussion

247.	A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called
A.	dry air
B.	moist air
C.	saturated air
D.	specific humidity
Answer» D. specific humidity

Discussion

248.	The final relative humidity of the air during cooling and dehumidification is generally __________ than that of entering air.
A.	lower
B.	higher
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

249.	For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is
A.	zero
B.	20
C.	50
D.	100
Answer» E.

Discussion

250.	The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to
A.	Stanton number
B.	Biot number
C.	Peclet number
D.	Grashoff number
Answer» B. Biot number

Discussion

Explore topic-wise MCQs in Automobile Engineering.

The lowest thermal diffusivity is of

According to Stefan's law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature.

The dry bulb temperature lines, on the psychrometric chart are

The dry bulb temperature during sensible heating of air

During humidification process, dry bulb temperature

A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be

The thermal diffusivity for gases is generally __________ those for liquids.

The boiling point of __________ is -10.5°C.

Air refrigerator works on

During sensible cooling of air, specific humidity

The radiation emitted by a black body is known as

In a vapour compression system, the condition of refrigerant is dry saturated vapour

The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat.

Dehydration is the process of removing water vapour from the surrounding air.

The sensible heat gain is due to the __________ difference between the fresh air and the air in space.

The expression is used for calculating relative humidity.

The specific humidity during cooling and dehumidification

In a psychrometric chart, dew point temperature lines are horizontal and non-uniformly spaced.

In a psychrometric chart, specific humidity (moisture content) lines are

A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is

The lowest temperature during the cycle in a vapour compression system occurs after

In a refrigeration system, the expansion device is connected between the

Which of the following refrigerant has the lowest freezing point?

A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.

Hydrogen is used in electrolux refrigeration system so as to __________ the rate of evaporation of the liquid ammonia passing through the evaporator.

The alignment circle is marked on the psychrometric chart at

A simple air cooling system is good for __________ flight speeds.

In chemical dehumidification process,

In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by

The undesireable property of a refrigerant is

The sensible heat during humidification process decreases.

An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

The super-heating in a refrigeration cycle

The emissivity of a polished silver body is __________ as compared to black body.

The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is

It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be

The refrigerant supplied to a compressor must be

The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and

The expansion valve in a refrigerator controls the flow of refrigerant.

In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about

The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called

The overall coefficient of heat transfer is used in problems of

Thermal conductivity of a material may be defined as the

According to Newton's law of cooling, the heat transfer from a hot body to a cold body is

In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is

A vapour absorption refrigerator uses __________ as a refrigerant.

A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called

The final relative humidity of the air during cooling and dehumidification is generally __________ than that of entering air.

For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is

The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to